Vehicle lifts fitted to vehicles have long been known. They serve to convey articles or people from the interior of the vehicle to the exterior and back again if there is a difference in level between the level of the interior of the vehicle and the location at which the articles or people are to be placed, or if there is a gap which has to be bridged over. An important application for such vehicle lifts is in vehicles in which wheelchair users are transported. Such a vehicle lift of the general kind set forth, to the present applicant, is disclosed for example in DE 203 09 868 U1.
Known vehicle lifts have a platform which is pivoted movably to at least one support pillar and is moved by means of a lifting device. In general a distinction can be drawn between at least two main positions. The first retracted position is the retracted position, during which the vehicle lift is not used. The platform is then generally in a vertical position so that the entire vehicle lift takes up as little room and space as possible and does not interfere while travelling with the vehicle.
In the second extended position, the vehicle lift is extended and the platform is disposed substantially horizontally near the ground so that for example a wheelchair user can easily move from the ground on to the platform. In most cases, there is also an intermediate position in which the platform is approximately at the level of a vehicle interior so that for example a wheelchair user can travel from the platform into the vehicle interior. Between the intermediate position and the second extended position the platform is lowered substantially parallel to itself by means of the lifting device.
Consequently, for moving the vehicle lift from the retracted to the extended position, the platform, on the one hand, has to be moved from the vertical position into the horizontal position and, on the other hand, it has to be lowered to a ground level so that, for example, wheelchair users can easily roll onto the platform. In that respect, it is desirable for the lifting devices to provide adequate power to lift relatively heavy loads by means of the vehicle lift, while also being of dimensions which are as small as possible so that weight and power consumption of the vehicle lift are low. A critical point in that respect is the start of moving the vehicle lift from the first retracted position to the second extended position.
In known lift devices, for example, coil springs are used to lower weight and power consumption. For instance, coil springs engage a pivot connection point between the lifting device and the corresponding vehicle to assist with the movement of the vehicle lift from the first retracted position to the second extended position. However, these coil springs have to be of large dimensions because of the high moments required. On the other hand, such coil springs can suffer from defects, for example, due to fatigue, which requires dismantling substantially the entire lift for maintenance or replacement of the springs. Such maintenance or replacement is often complicated, expensive, and generally undesirable.
Therefore the object of the present invention is to provide a vehicle lift of the kind set forth in the opening part of this specification, which is at least improved in respect of one of the above-mentioned problems. In particular the object of the invention is to provide a vehicle lift which can be reliably and effectively moved from the first retracted position to the second extended position and which also involves a low level of maintenance.